The invention relates to a perfluoropolyether having improved thermostability over the presently available perfluoropolyethers, to a process therefor, and to a process therewith.
Hereinafter trademarks or trade names are shown in upper case characters.
Perfluoropolyethers (hereinafter PFPE) are fluids having important uses in oils and greases for use under extreme conditions. A property shared by the class is extreme temperature stability in the presence of oxygen and they find use in tribological or lubrication applications. Among their advantages as extreme lubricants is the absence of gums and tars among the thermal decomposition products. In contrast to the gum and tar thermal degradation products of hydrocarbons, the degradation products of PFPE fluids are volatile. In actual use, the upper temperature limit is determined by the stability of the oil or grease. Lewis acids, metal fluorides such as aluminum trifluoride or iron trifluoride, are formed as a result of heat at microscale loci of metal to metal friction; for instance as stationary bearings are started in motion. Thus the PFPE stability in the presence of the metal fluoride, although lower than the stability in the absence of the metal fluoride, establishes the upper performance temperature. The three commercial PFPEs, KRYTOX (from E. I. du Pont de Nemours and Company, Inc., Wilmington Del.), FOMBLIN and GALDEN (from Ausimont/Montedison, Milan, Italy) and DEMNUM (from Daikin Industries, Osaka, Japan) differ in chemical structure. A review of KRYTOX is found in Synthetic Lubricants and High-Performance Fluids, Rudnick and Shubkin, Eds., Marcel Dekker, New York, N.Y., 1999 (Chapter 8, pp. 215-237). A review of FOMBLIN and GALDEN is found in Organofluorine Chemistry, Banks et al., Eds., Plenum, New York, N.Y., 1994, Chapter 20, pp. 431-461, and for DEMNUM, in Organofluorine Chemistry (op. cit.), Chapter 21, pp. 463-467.
The anionic polymerization of hexafluoropropylene epoxide as described by Moore in U.S. Pat. No. 3,332,826 can be used to produce the KRYTOX fluids. The resulting poly(hexafluoropropylene epoxide) PFPE fluids are hereinafter described as poly(HFPO) fluids. The initial polymer has a terminal acid fluoride, which is hydrolyzed to the acid followed by fluorination. The structure of a poly(HFPO) fluid is shown by Formula 1:
CF3xe2x80x94(CF2)2xe2x80x94Oxe2x80x94[CF(CF3)xe2x80x94CF2xe2x80x94O]sxe2x80x94Rfxe2x80x83xe2x80x83(Formula 1)
where s is 2-100 and Rf is a mixture of CF2CF3 and CF(CF3)2, with the ratio of ethyl to isopropyl terminal group ranging between 20:11 to 50:1.
DEMNUM fluids are produced by sequential oligomerization and fluorination of 2,2,3,3-tetrafluorooxetane (tetrafluorooxetane), yielding the structure of Formula 2.
Fxe2x80x94[(CF2)3xe2x80x94O]txe2x80x94Rf2xe2x80x83xe2x80x83(Formula 2)
where Rf2 is a mixture of CF3 or C2F5 and t is 2-200.
A common characteristic of the PFPE fluids is the presence of perfluoroalkyl terminal groups.
The mechanism of thermal degradation in the presence of a Lewis acid such as aluminum trifluoride has been studied. Kasai (Macromolecules, Vol. 25, 6791-6799, 1992) discloses an intramolecular disproportionation mechanism for the decomposition of PFPE containing xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94 linkages in the presence of Lewis acids.
FOMBLIN and GALDEN fluids are produced by perfluoroolefin photooxidation. The initial product contains peroxide linkages and reactive terminal groups such as fluoroformate and acid fluoride. These linkages and end groups are removed by ultraviolet photolysis and terminal group fluorination, to yield the neutral PFPE compositions FOMBLIN Y and FOMBLIN Z represented by Formulae 3 and 4, respectively
CF3O(CF2CF(CF3)xe2x80x94Oxe2x80x94)m(CF2xe2x80x94Oxe2x80x94)nxe2x80x94Rf3xe2x80x83xe2x80x83(Formula 3)
where Rf3 is a mixture of xe2x80x94CF3, xe2x80x94C2F5, and xe2x80x94C3F7; (m+n) is 8-45; and m/n is 20-1000; and
CF3O(CF2CF2xe2x80x94Oxe2x80x94)p(CF2xe2x80x94O)qCF3xe2x80x83xe2x80x83(Formula 4)
where (p+q) is 40-180 and p/q is 0.5-2. It is readily seen that Formulae 3 and 4 both contain the destabilizing xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94 linkage since neither n nor q can be zero. With this xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94 linkage in the chain, degradation within the chain can occur, resulting in chain fragmentation.
For PFPE molecules with repeating pendant xe2x80x94CF3 groups, Kasai discloses the pendant group provides a stabilizing effect on the chain itself and for the alkoxy end groups adjacent to a xe2x80x94CF(CF3)xe2x80x94. Absent the xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94 linkage, the PFPE is more thermally stable, but its eventual decomposition was postulated to occur at end away from the stabilizing xe2x80x94CF(CF3)xe2x80x94 group, effectively unzipping the polymer chain one ether unit at a time.
Therefore, there is substantial interest and need in increasing the thermal stability of PFPE fluids.
According to a first embodiment of the invention, a perfluoropolyether or a composition comprising thereof is provided, in which the perfluoropolyether comprises perfluoroalkyl radical end groups in which the radical has at least 3 carbon atoms per radical and is substantially free of perfluoromethyl and perfluoroethyl, and a 1,2-bis(perfluoromethyl)ethylene diradical, xe2x80x94CF(CF3)CF(CF3)xe2x80x94, is absent in the molecule of the perfluoropolyether.
According to a second embodiment of the invention, a process for improving the thermal stability of a perfluoropolyether is provided, which comprises modifying a process for producing a perfluoropolyether such that substantially all end groups of the perfluoropolyether have at least 3 carbon atoms per end group or, preferably, are C3-C6 branched and straight chain perfluoroalkyl end groups.
According to a third embodiment of the invention, a process is provided for producing a perfluoropolyether comprising perfluoroalkyl radical end groups in which the perfluoroalkyl radical has at least 3 carbon atoms per radical as disclosed in the first embodiment of the invention. The process can comprise (1) contacting a perfluoro acid halide, a C2 to C4-substituted ethylene epoxide, a C3+ fluoroketone, or combinations of two or more thereof with a metal halide to produce an alkoxide; (2) contacting the alkoxide with either hexafluoropropylene oxide or 2,2,3,3-tetrafluorooxetane to produce a second acid halide; (3) esterifying the second acid halide to an ester; (4) reducing the ester to its corresponding alcohol; (5) converting the corresponding alcohol with a base to a salt form; (6) contacting the salt form with a C3 or higher olefin to produce a fluoropolyether; and (7) fluorinating the fluoropolyether.
According to a fourth embodiment of the invention, a thermally stable grease or lubricant is provided, which comprises a thickener with a perfluoropolyether of composition thereof disclosed in the first embodiment of the invention.
This invention is directed to a thermal stable perfluoropolyether (or PFPE) composition and processes for making and using the composition. The term xe2x80x9cperfluoropolyetherxe2x80x9d and xe2x80x9cPFPE fluidxe2x80x9d (xe2x80x9cPFPExe2x80x9d or xe2x80x9cPFPE fluidsxe2x80x9d) are, unless otherwise indicated, exchangeable.
According to the first embodiment of the invention, there is provided a perfluoropolyether comprising branched or straight chain perfluoroalkyl radical end groups, each of which has at least 3 carbon atoms per radical, is substantially free of perfluoromethyl and perfluoroethyl end groups and does not contain any 1,2-bis(perfluoromethyl)ethylene diradicals [xe2x80x94CF(CF3)CF(CF3)xe2x80x94] in the chain. The term xe2x80x9csubstantiallyxe2x80x9d, as used herein, refers to a perfluoropolyether or PFPE fluid of this invention having only trace C1-C2 perfluoroalkyl endgroups such that the initial decomposition in a specific use is inconsequential and tolerable. An unavoidable trace of remaining perfluoropolyether or PFPE molecules with a perfluoro-methyl or -ethyl end group, while not desirable, may be tolerable as such molecules degrade to volatile products, leaving the more stable PFPE molecules. Thus thermal stability increases after some initial degradation.
The preferred perfluoropolyethers have the formula of CrF(2r+1)xe2x80x94Axe2x80x94CrF(2r+1) in which each r is independently 3 to 6; if r=3, both end groups CrF(2r+1) are perfluoropropyl radicals; A can be Oxe2x80x94(CF(CF3)CF2xe2x80x94O)w, Oxe2x80x94(CF2xe2x80x94O)x(CF2CF2xe2x80x94O)y, Oxe2x80x94(C2F4xe2x80x94O)x, Oxe2x80x94(C2F4xe2x80x94O)x(C3F6xe2x80x94O)y, Oxe2x80x94(CF(CF3)CF2xe2x80x94O)x(CF2xe2x80x94O)y, O(CF2CF2CF2O)w, Oxe2x80x94(CF(CF3)CF2xe2x80x94O)x(CF2CF2xe2x80x94O)yxe2x80x94(CF2xe2x80x94O)z, or combinations of two or more thereof; preferably A is Oxe2x80x94(CF(CF3)CF2xe2x80x94O)w, Oxe2x80x94(C2F4xe2x80x94O)x, O(C2F4O)x,(C3F6xe2x80x94O)y, Oxe2x80x94(CF2CF2CF2xe2x80x94O)x, or combinations of two or more thereof; w is 4 to 100; x, y, and z are each independently 1 to 100.
Such compositions, as illustrated in the EXAMPLES section, show a significant increase in thermal stability over the corresponding PFPE fluids having perfluoroethyl or perfluoromethyl end groups. Similarly, stability of those PFPE fluids subject to degradation at the perfluoroalkyl terminal group, in addition to those based on poly(HFPO), can be improved by replacing xe2x80x94CF3 and xe2x80x94C2F5 groups with, for example, C3-C6 perfluoroalkyl groups.
According to the second embodiment of the invention, a process for improving the thermal stability of a perfluoropolyether is provided. The process can comprise (1) incorporating one C3+ terminal segment into a perfluoropolyether precursor to produce a precursor having an initial C3+ end group; (2) polymerizing the precursor having an initial C3+ end group to a desired molecular weight polymer containing an alkoxide growing chain; (3) incorporating a second C3+ end group to produce a polyether having both C3+ end groups; and (4) fluorinating the polyether having both C3+ end groups. The term xe2x80x9cC3+xe2x80x9d refers to 3 or more carbon atoms.
Several processes are available for producing a PFPE fluid having improved thermal stability. The process is more fully disclosed in the third embodiment of the invention, other similar processes are evident to those skilled in the art. For example purposes, poly(HFPO) fluids are subject to exacting fractional distillation under vacuum. In practice, the upper molecular weight limit for such a distillation is the separation and isolation of F(CF(CF3)xe2x80x94CF2xe2x80x94O)9xe2x80x94CF2CF3 and F(CF(CF3)xe2x80x94CF2xe2x80x94O)9xe2x80x94CF(CF3)2. The increased thermal stability of free fluids with perfluoropropyl and perfluorohexyl end groups over those with perfluoroethyl end groups, described in the EXAMPLES, demonstrates the present invention.
The invention discloses perfluoropolyether having preferred C3-C6 perfluoroalkyl ether end groups. It is, however, within the scope of the invention that the disclosure is also applicable to any C3+ perfluoroalkyl ether end group. In the case of KRYTOX, for instance, the resultant poly(HFPO) chain terminates at both ends with C3-C6 perfluoroalkyl groups, having the formula of
CrF(2r+1)xe2x80x94Oxe2x80x94[xe2x80x94CF(CF3)xe2x80x94CF2xe2x80x94Oxe2x80x94]sxe2x80x94CrF(2r+1)xe2x80x83xe2x80x83(Formula 5)
According to the third embodiment of the invention, a process for producing a preferred perfluoropolyether in which substantially all perfluoroalkyl end groups of the perfluoropolyether contain at least three, preferably 3 to 6, carbon atoms per end group. The preferred perfluoropolyether has the formula of CrF(2r+1)xe2x80x94Axe2x80x94CrF(2r+1) as disclosed in the first embodiment of the invention. The process can comprise (1) contacting a perfluoro acid halide, a C2 to C4-substituted ethylene epoxide, a C3+ fluoroketone, or combinations of two or more thereof with a metal halide to produce an alkoxide; (2) contacting the alkoxide with either hexafluoropropylene oxide or tetrafluorooxetane to produce a second acid fluoride; (3) contacting the second acid fluoride with an alcohol to produce an ester; (4) reducing the ester to corresponding alcohol: (5) contacting the corresponding alcohol with a base to a salt form; (6) contacting the salt form with a C3+ or higher olefin to produce a fluoropolyether; and (7) fluorinating the fluoropolyether to produce the perfluoropolyether of the invention.
Typically, one C3+ terminal segment is produced first (the xe2x80x9cinitial end groupxe2x80x9d) followed by its polymerization using, for example, hexafluoropropylene oxide or tetrafluorooxetane to a desired molecular weight polymer. This polymer is thermally treated to convert the growing alkoxide chain to an acid fluoride. The acid fluoride is converted to an ester, which is then reduced to its corresponding alcohol. The second C3+ terminal group (the xe2x80x9cfinal end groupxe2x80x9d) is now incorporated into the polymer by, for example, treatment with a mineral base in a suitable solvent and the addition of a reactive hydro- or fluoro-olefin. Reactive hydroolefins include allyl halides and tosylates. Finally the PFPE is formed by replacing essentially all hydrogen atoms with fluorine atoms.
Process 1 discloses a process for producing PFPEs terminated with paired normal C3 to C6 end groups. The process comprises (1) contacting a perfluoro acid halide or a C2 to C4-substituted ethylene epoxide with a metal halide to produce an alkoxide; (2) contacting the alkoxide with either hexafluoropropylene oxide or tetrafluorooxetane to produce a second acid halide; (3) contacting the second acid halide with an alcohol to produce an ester; (4) reducing the ester to corresponding alcohol: (5) contacting the corresponding alcohol with a base to a salt form; (6) contacting the salt form with a C3+ olefin to produce a fluoropolyether; and (7) fluorinating the fluoropolyether to produce the perfluoropolyether of the invention. The preferred halide, unless otherwise indicated, is fluoride and the preferred base is a metal hydroxide such as, for example, alkali metal hydroxide as used below to illustrate these steps.
Step 1 involves the contact of either a C3-C6 perfluoro acid fluoride or a C2 to C4 substituted ethylene epoxide with a metal fluoride, such as CsF or KF, in a suitable solvent such as tetraethylene glycol dimethyl ether at temperatures from about 0xc2x0 to about 100xc2x0 C. to form an alkoxide which can be further polymerized. 
where preferred M is a metal such as cesium or potassium, Rf4 is CaF(2a+1), a is 2 to 5, Rf1 is CbF(2b+1), and b is 1 to 4.
Step 2 involves the contact of the alkoxide with either hexafluoropropylene oxide or tetrafluorooxetane at low temperature, about xe2x88x9230 to about 0xc2x0 C., followed by thermolysis at  greater than 50xc2x0 C., to produce the PFPE with one C3-C6 end group and an acid fluoride on the other terminus, and having the Formula 6 (from HFPO) or Formula 7 (from tetrafluorooxetane).
(C3-C6 Segment)(HFPO)sCF(CF3)COFxe2x80x83xe2x80x83(Formula 6)
or
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2COF,xe2x80x83xe2x80x83(Formula 7)
The (C3-C6 Segment) is defined C3-C6 perfluoroalkyl group having an oxygen between the segment and the polymer repeat unit.
Alternatively, Formula 7 can be converted to an equivalently useful acid fluoride by replacing all methylene hydrogen radicals with fluorine radicals using the fluorination procedure disclosed in Step 7, with or with out the use of a suitable solvent, at temperatures of about 0 to about 180xc2x0 C., and with autogenous or elevated fluorine pressures of 0 to 64 psig (101 to 543 kPa). The resulting perfluorinated acid fluoride is then further processed as follows.
(C3-C6 Segment)(CH2CF2CF2O)sCH2CF2COF+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)sCF2CF2COF.
Step 3 involves the contact of the acid fluoride with an alcohol such as methanol, with or without solvent or excess alcohol, at a temperature of about 0 to about 100xc2x0 C., producing the corresponding ester. The HF produced can be removed by washing with water.
(C3-C6 Segment)(HFPO)sCF(CF3)COF+R1OHxe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)COOR1,
(C3-C6 SEGMENT)(CH2CF2CF2O)TCH2CF2COF+R1OHxe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2COOR1,
where R1 is alkyl and preferably methyl.
In Step 4, the ester is reduced with a reducing agent such as, for example, sodium borohydride or lithium aluminum hydride in a solvent such as an alcohol or THF (tetrahydrofuran) at a range of temperatures (0 to 50xc2x0 C.) and at autogenous pressure for a time period of from about 30 minutes to about 25 hours to produce the corresponding alcohol (PFPE precursor):
(C3-C6 Segment)(HFPO)sCF(CF3)COOR1+NaBH4xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OH,
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2COOR1+NaBH4xe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OH.
In Step 5, the PFPE precursor alcohol is converted to a metal salt. The conversion can be effected by contacting the precursor alcohol with a metal hydroxide, optionally in a solvent, under a condition sufficient to produce the metal salt. The presently preferred metal hydroxide includes alkali metal hydroxides such as, for example, potassium hydroxide and alkaline earth metal hydroxides. Any solvent, such as, for example, acetonitrile, that does not interfere with the production of the metal salt can be used. Suitable condition include a temperature in the range of from about 20 to about 100xc2x0 C. under a pressure of about 300 to about 1,000 mmHg (40-133 kPa) for about 30 minutes to about 25 hours.
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OH+M1OHxe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OM1,
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OH+M1OHxe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OM1,
where M1 is an alkali metal, an alkaline earth metal, or ammonium.
In Step 6, the metal salt is contacted with an olefin to produce a C3-C6 segment fluoropolyether. The contacting can be carried out in the presence of a solvent such as, for example, an ether or alcohol, under a condition to produce a fluoropolyether that can be converted to perfluoropolyether of the invention by fluorination disclosed herein below. Any olefin having more than three carbon atoms, preferably 3 to 6, can be used. The olefin can also be substituted with, for example, a halogen. Examples of such olefins include, but are not limited to, hexafluoropropylene, octafluorobutene, perfluorobutylethylene, perfluoroethylethylene, perfluorohexene, allyl halides, and combinations of two or more thereof. Additionally, a C3-C6 segment containing a moiety known in the art to be a good leaving group in nucleophilic displacement reactions, for example tosylates, can also be used. The contacting conditions can include a temperature in the range of from about 0 to about 100xc2x0 C. under a pressure in the range of from about 0.5 to about 64 psig (105-543 kPa) for about 30 minutes to about 25 hours.
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OM1+Rf1CFxe2x95x90CF2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCF2CFHRf1+(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCFxe2x95x90CFRf1; or
(C3-C6 Segment)(HFPO)sCF(CF3) CH2OM1+X1CHR2CHxe2x95x90CH2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CHxe2x95x90CHR2 where R2 is CcH(2c+1), c is 0 to 3, and X1 is a halogen; or
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OM1+Rf5CF2CHxe2x95x90CH2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CH2CF2Rf5+(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CHxe2x95x90CFRf5 where Rf5 is CcF(2c+1); or
(C3C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OM1+Rf1CFxe2x95x90CF2xe2x86x92Rf1CFxe2x95x90CF2xe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCF2CFHRf1+(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCFxe2x95x90CFRf1; or
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OM1+X1CHR2CHxe2x95x90(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCH2CHxe2x95x90CHR2; or
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OM1+Rf5CF2CHxe2x95x90CH2xe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCH2CH2CF2Rf5+(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCH2CHxe2x95x90CFRf5.
In Step 7, the perfluoropolyether with paired C3 to C6 segments is formed with elemental fluorine using any technique known to one skilled in the art such as disclosed in Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Vol. 11, page 492 and references therein.
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCF2CFHRf1+(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCFxe2x95x90CFRf1+F2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CF2OCF2CF2Rf1; or
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CHxe2x95x90CHR2+F2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CF2OCF2CF2CF2Rf5; or
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CH2CF2Rf5+(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH2CHxe2x95x90CFRf1+F2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CF2OCF2CF2CF2Rf5; or
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCF2CFHRf1+(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCFxe2x95x90CFRf1+F2xe2x86x92(C3xe2x80x94C6 Segment)(CF2CF2CF2O)sCF2CF2CF2OCF2CF2Rf1; or
(C3C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OCH2CHxe2x95x90CHR 2+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CF2OCF2CF2CF2Rf5; or
(C3-C6 Segment)(CH2CF2CF2O)TCH2CF2CH2OCH2CH2CF 2RF5+(C3-C6 Segment)(CH2CF2CF2O)TCH2CF2CH2OCH2CHxe2x95x90CFR F5+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CF2OCF2CF2CF2R f5.
Process 2 discloses the synthesis of PFPEs terminated with a normal C3 to C6 initial end group and a branched C3 to C6 final end group. Steps 1 to 5 are the same as those in Process 1. The terminal fluoroalkene or allyl halide in Step 6 is replaced with a branched fluoroalkene such as 2-perfluorobutene or a branched allyl halide such as 1-bromo-2-butene. Step 7 is as described in Process 1.
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OH+M1OH+Rf6CFxe2x95x90CFRf7xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCF(Rf6)CFHRf7+(C3-C6 Segment)(HFPO)sCF(CF3)CH2OC(Rf6)xe2x95x90CFRf7 where Rf6 is C eF(2e+1),Rf7 is CfF(2f+1), such that e and fxe2x89xa70, (e+f)xe2x89xa64 and (e+f)xe2x89xa71; or
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OH+M1OH+X1CR4CHxe2x95x90CHR5xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2OCH(R5)CHxe2x95x90CHR4 where R4 is CgH(2g+1)R5 is ChH(2h+1), such that g and hxe2x89xa70 and (g+h) is 1 to 3.
Process 3A discloses the synthesis of PFPEs terminated with a branched C3 to C6 initial end group and a normal C3 to C6 final end group. The reagents, either the acid fluoride or epoxide, in Step 1 of Process 1, are replaced with a C3 to C6 fluoroketone. Then, steps 2 to 7 of Process 1 are used.
Rf8C(O)Rf9+MFxe2x86x92Rf8(Rf9)CFOxe2x80x94M+, where Rf8 is CjF(2j+1), Rf9 is CkF(2k+1), such that j and kxe2x89xa71, (j+k)xe2x89xa65.
Process 3B discloses the synthesis of PFPEs terminated with paired branched C3 to C6 end groups. Step 1 of Process 3 is practiced, followed by Steps 2 to 5 of Process 1, followed by Step 6 of Process 2A, and then finally Step 7 of Process 1.
Process 4 discloses the synthesis of PFPEs terminated with a C3 to C6 initial end group and a C3 to C6 final end group. Steps 1 to 3 of Process one; or Steps 1 of Process 3A and steps 2 and 3 of Process 1 are followed. The ester is then contacted with a Grignard Reagent of the type C2H5M2X1 or CH3M2X1, where M2 is magnesium or lithium, forming the carbinol which can either be dehydrated or fluorinated directly in Step 7 as described in Process 1 to the desired PFPE. Steps 4 through 6 disclosed in Process 1 are omitted.
(C3-C6 Segment)(HFPO)sCF(CF3)C(O)OR1+2R6M2X1xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)C(OH)(R6)2,
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2COOR1+2R6M2X1xe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2C(OH)(R6)2,
where R6 is CH3 or C2H5 such that the total number of carbons in the final segment is 3 to 6 and (R6)2 always means no more than one CH3 and one C2H5.
Alternatively, (C3-C6 Segment)(CF2CF2CF2O)tCF2CF2COOR1+2R6M2X1xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2C(OH)(R6)2.
Process 5 discloses an additional procedure for making PFPEs with a C3-C6 initial end group with a branched or normal C3-C6 final end group, which comprises (1) contacting a PFPE acid fluoride precursor prepared in steps 1 and 2 of Process 1 or steps 1 and 2 of Process 3 with a metal iodide such as, for instance, lithium iodide at an elevated temperatures such as, for example, at least 180xc2x0 C., or at least 220xc2x0 C., to produce a corresponding iodide; (2) either replacing the iodine radical with a hydrogen radical using a suitable reducing agent such as, for example, sodium methylate at temperatures of about 25xc2x0 C. to about 150xc2x0 C. and autogenous pressure alone or reacting said iodide with a C2 to C4 olefin using a peroxide or azo catalyst or zero valent metal catalyst, or dehydrohalogenating the iodide/olefin adduct in alcoholic solvent; and (3) fluorinating the corresponding products to produce the desired perfluoropolyether.
Process 5 Step 1
(C3-C6 Segment)(HFPO)sCF(CF3)COF+LiIxe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)I+LiF+CO,
(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2COF+LiIxe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2I+LiF+CO,
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)COF+LiIxe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)I+LiF+CO;
(C3-C6 Segment)(HFPO)sCF(CF3)COF+LiI xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2I+CF3COF+LiF+CO;
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)COF+LiI xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2I+CF3COF+LiF+CO.
Process 5 Step 2A
(C3-C6 Segment)(HFPO)sCF(CF3)I+CX2xe2x95x90CXR7xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CX2CXIR7 where Xxe2x95x90H or F, R7=CdX(2d+1), d=0 to 2;
(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2I+CX2xe2x95x90CXR7xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CX2CXIR7;
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)I+CX2xe2x95x90CXR7xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)CX2CXIR7;
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3) CF2I+CX2xe2x95x90CXR8xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CX2CXIR8 where R8=CvX(2v+1), v=0 to 1;
{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2I+CX2xe2x95x90CXR8xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2CX2CXIR8.
Process 5 Step 2A1, When One X of the Terminal Methylene From the Olefin of Process 5 Step 2A was Hydrogen
(C3-C6 Segment)(HFPO)sCF(CF3)CX2CXIR7+M1OHxe2x86x92(C3-C6 Segment) (HFPO)sCF(CF3)CXxe2x95x90CXR7; or
(C3-C6 Segment)(CF2CF2CF2O)sCF2CF2CX2CXIR7+M1OHxe2x86x92(C3-C6 Segment)(CF2CF2CF2O)sCF2CF2CXxe2x95x90CXR7; or
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)CX2CXIR8+M1OHxe2x86x92{Rf8(Rf9)CFO Segment} (HFPO)sCF(CF3)CXxe2x95x90CXR8; or
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CX2CXIR8+M1OHxe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CXxe2x95x90CXR8; or
{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2CX2CXIR8+M1OHxe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2CXxe2x95x90CXR8.
Process 5 Step 2B
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2I+NaOCH3/HOCH3xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2H, or
{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2I+NaOCH3/HOCH3xe2x86x92{Rf8(Rf9)CO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2H.
Process 5 Step 3A
(C3-C6 Segment (HFPO)(sxe2x88x921)CF(CF3)CF2I+F2xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF3; or
{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2I+F2xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF3.
Process 5 Step 3B
(C3-C6 SEGMENT)(HFPO)(Sxe2x88x921)CF(CF3)CF2H+F2xe2x86x92(C3-C6 SEGMENT)(HFPO)(Sxe2x88x921)CF(CF3)CF3; OR
{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2H+F2xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF3.
Process 5 Step 3C
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CX2CXIR7+F2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CF2CF2 Rf10, where Rf10=CdF(2d+1), or
(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CX2CXIR7+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CF2CF2Rf10; or
{Rf8(Rf9)CO Segment}(HFPO)sCF(CF3)CX2CXIR7+F2xe2x86x92{Rf8(Rf9)CO Segment}(HFPO)sCF(CF3)CF2CF2Rf10;or
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CX2CXIR7+F2xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CF2CF2Rf11 where Rf 11=Cv
{RF8(RF9)CO SEGMENT}(HFPO)(Sxe2x88x921)CF(CF3)CF2CX2CXR8+F2xe2x86x92{RF8(RF9)CO SEGMENT}(HFPO)(Sxe2x88x921)CF(CF3)CF2CF2CF2RF11.
Process 5 Step 3D
(C3-C6 Segment)(HFPO)(s)CF(CF3)CXxe2x95x90CXR7+F2xe2x86x92(C3-C6 Segment)(HFPO)(s)CF(CF3)CF2CF2 Rf10; or
(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CXxe2x95x90CXR7+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CF2CF2Rf10; or
{Rf8(Rf9)CO Segment}(HFPO)sCF(CF3)CXxe2x95x90CXR7+F2xe2x86x92{Rf8(Rf9)CO Segment}(HFPO)sCF(CF3)CF2CF2Rf10; or
(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CXxe2x95x90CXR8+F2xe2x86x92(C3-C6 Segment)(HFPO)(sxe2x88x921)CF(CF3)CF2CF2CF2Rf11, or
{RF8(RF9)CO SEGMENT}(HFPO)(Sxe2x88x921)CF(CF3)CF2CXxe2x95x90CXR8+F2xe2x86x92{Rf8(Rf9)CO Segment}(HFPO)(sxe2x88x921)CF(CF3)CF2CF2CF2Rf11.
Process 6 discloses the synthesis of PFPEs terminated with C3-C6 end groups by the fluorination of corresponding hydrocarbon polyethers, following the process described in Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Vol. 11. pages 492 and specifically as described by Bierschenk et al. in U.S. Pat. Nos. 4,827,042, 4,760,198, 4,931,199, and 5,093,432, and using the suitable starting materials with the proper end groups, compositions disclosed can be prepared.
The hydrocarbon polyether can be combined with an inert solvent such as 1,1,2-trichlorotrifluoroethane to produce a fluorination mixture, optionally in the presence of a hydrogen fluoride scavenger such as sodium or potassium fluoride. A fluid mixture containing fluorine and an inert diluent such as nitrogen can be introduced to the fluorination mixture for a sufficient period of time to convert essentially all hydrogen atoms to fluorine atoms. The flow rate of the fluid can be in the range of from about 1 to about 25000 ml/min, depending on the size of the fluorination mixture. The fluoropolyether can also be introduced after the introduction of the fluorine-containing fluid at a rate such that a perfluorination of the fluoropolyether can be accomplished.
CrH(2r+1)Oxe2x80x94(CH(CH3)CH2xe2x80x94O)wCrH(2r+1)+F2xe2x86x92CrF(2r+1)Oxe2x80x94(CF(CF3)CF2xe2x80x94O)wCrF(2r+1);
CrH(2r+1)Oxe2x80x94(C2H4xe2x80x94O)wCrH(2r+1)+F2xe2x86x92CrF(2r+1)Oxe2x80x94(C2F4xe2x80x94O)wCrF(2r+1);
CrH(2r+1)Oxe2x80x94(C2H4xe2x80x94O)w(C3H6xe2x80x94O)wCrH(2r+1)+F2xe2x86x92CrF(2r+1)Oxe2x80x94(C2F4xe2x80x94O)w(C3F6xe2x80x94O)wCrF(2r+1);
CrH(2r+1)Oxe2x80x94(CH2CH2CH2xe2x80x94O)w(CH(CH3)CH2xe2x80x94O)uCrH(2r+1)+F2xe2x86x92CrF(2r+1)Oxe2x80x94(CF2CF2CF2xe2x80x94O)w(CF(CF3)CF2xe2x80x94O)uCrF(2r+1) where u is 0 to 100.
Process 7 discloses the synthesis of PFPEs terminated with a C3 to C6 initial end group and a branched C3 final end group. The reagents are those described in steps 1 to 4 of Process 1, or in step 1 of Process 3, followed by steps 2 to 4 of Process 1 to provide a starting alcohol. An alcohol having either branched or normal starting end can be reacted with sulfur tetrafluoride (SF4) or a derivative of SF4 such as N,N,-diethylaminosulfur trifluoride or a phosphorus pentahalide PX25 such as phosphorous pentabromide, where X2 is Br, Cl, or F at temperatures of about 25 to about 150xc2x0 C. and autogenous pressure with or without solvent gives the terminal dihydrohalide which can be fluorinated according to step 7 of process 1, as illustrated below.
(C3-C6 Segment)(HFPO)sCF(CF3)CH2OH+SF4xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)CH2F,
(C3-C6 Segment)(HFPO)sCF(CF3)CH2F+F2xe2x86x92(C3-C6 Segment)(HFPO)sCF(CF3)2,
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)CH2OH+SF4xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)CH2F;
{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)CH2F+F2xe2x86x92{Rf8(Rf9)CFO Segment}(HFPO)sCF(CF3)2.
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2OH+SF4xe2x86x92(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2F
(C3-C6 Segment)(CH2CF2CF2O)tCH2CF2CH2F+F2xe2x86x92(C3-C6 Segment)(CF2CF2CF2O)tCF2CF2CF3.
Process 8 discloses the synthesis of PFPEs terminated with a C3 to C6 initial end group and specifically a perfluorotertiary final end group. Here, either a salt of any fluorotertiary alcohol such as perfluoro-t-butanol, or perfluoro-t-butyl hypofluorite is reacted with any fluoropolyether with a starting C3-C6 or Rf8(Rf9)CFO segment and either a xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CF2 or xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CHF terminus as shown. The resulting product is then fluorinated, if necessary.
(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CF2+M1OC(CF3)3xe2x86x92(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94CH(CF3)CF2OC.(CF3)3,
(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94CH(CF3)CF2OC(CF3)3+F2xe2x86x92(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94CF(CF3)CF2OC(CF3)3,
{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CF2+M1OC(CF3)3xe2x86x92{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94CH(CF3)CF2OC(CF3)3,
{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94CH(CF3)CF2OC(CF3)3+F2xe2x86x92{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94CF(CF3)CF2OC(CF3)3,
(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CF2+FOC(CF3)3xe2x86x92(C3-C6 Segment)xe2x80x94Axe2x80x94Oxe2x80x94CF(CF3)CF2OC(CF3)3,
{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94C(CF3)xe2x95x90CF2+FOC(CF3)3xe2x86x92{Rf8(Rf9)CFO Segment}xe2x80x94Axe2x80x94Oxe2x80x94CF(CF3)CF2OC(CF3)3 
While the procedures for replacing end groups with C3-C6 end groups can also be practiced on the FOMBLIN fluids described above, the value of inserting the more stable end groups is severely limited due to the presence of the chain destabilizing xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94 segments therein.
The PFPE fluids of the invention can be purified by any means known to one skilled in the art such as contact with absorbing agents, such as charcoal or alumina, to remove polar materials and fractionated conventionally by distillation under reduced pressure by any method known to one skilled in the art.
According to the fourth embodiment of the invention, a thermally stable grease or lubricant composition is provided. Greases containing the perfluoropolyether disclosed in the first embodiment of the invention can be produced by combining the perfluoropolyether with a thickener. Examples of such thickeners include, but are not limited to, standard thickeners such as, for example, poly(tetrafluoroethylene), fumed silica, and boron nitride, and combinations of two or more thereof. The thickeners can be present in any appropriate particle shapes and sizes as known to one skilled in the art.
According to the invention, the perfluoropolyether of the invention can be present in the composition in the range of from about 0.1 to about 50, preferably 0.2 to 40, percent by weight. The composition can be produced by any methods known to one skilled in the art such as, for example, by blending the perfluoropolyether with the thickener.